Synthesis and evaluation of P-chirogenic monodentate binaphthyl phosphines

P-Chirogenic monodentate binaphthyl phosphines were prepared in five steps from enantiomerically pure BINOL. This approach supposes the utilization of two methods previously developed in our group, the formation of secondary phosphine oxide, and the reduction of tertiary phosphine oxide using the association of tetramethyldisiloxane and Ti(OⁱPr)₄. During the last reduction step, only the formation of the more stable diastereoisomer was observed. This product was employed as a ligand for the palladium catalyzed hydrosilylation of styrene to afford the corresponding alcohol with high yield and enantiomeric excess.     

First-principle predictions of basicity of organic amines and phosphines in acetonitrile

Amines and phosphines are widely utilized as bases and basic organocatalysts in organic chemistry. Thus it is highly valuable to develop a coherent theoretical method that can accurately predict the basicity of structurally unrelated amines and phosphines in organic solvents from the first principles. Herein we developed the first ab initio protocol that could predict the pK_a value of any protonated amine or phosphine in acetonitrile through systematic benchmarking. By comparing to a variety of available experimental data (total number=98), it was determined that the precision of the optimized method in basicity prediction was as low as 1.1 pK_a unit. With the powerful new method in hand, we subsequently conducted some systematic studies about the basicity of organic amines and in particular phosphines, for which very few experimental data were available. It was found that the solvent exerted profound effects on the basicity of amines and phosphines. Accordingly we concluded that it was not valid to use gas-phase data to interpret the solution-phase basicity of amines and phosphines. Next we reported the basicity of a number of synthetically important aliphatic and aromatic amines and phosphines in acetonitrile. We also compared, for the first time, the α-substituent effects on the basicity of aliphatic amines and phosphines and the remote substituent effects on the basicity of aromatic amines and phosphines. Finally, we studied for the first time the basicity of cyclic amines and phosphines. It was found that the ring strain exerted some interesting effects on the basicity of amines and phosphines.     

Synthesis of non-hydrolyzable substrate analogs for Asp-tRNA/Glu-tRNA amidotransferase

Non-hydrolyzable substrate analogs for tRNA-dependent amidotransferase, 2′- or 3′-aspartyl or -glutamyl adenosine, were synthesized from adenosine without protection of the adenine base. The hydroxyl groups of adenosine were selectively protected, followed by a series of oxidation/reductions to alter the stereochemistry. DFT calculations revealed the driving forces for the ketone hydrate formation at C-2′, but not the C-3′ carbon during the oxidation step. Subsequently, triflation and azide replacement yielded azidoadenosines, which were coupled to protected amino acids after deprotection and reduction. After global deprotection, the target substrate analogs were obtained in 2–14% overall yields from adenosine.     

Reduction of phosphine oxides to phosphines with the InBr3/TMDS system

An efficient method for the reduction of phosphine oxide derivatives into their corresponding phosphines is described. The system InBr₃/TMDS allows the reduction of different secondary and tertiary phosphine oxides as well as aliphatic and aromatic phosphine oxides.     

Formation and Properties of Hydrogenation Catalysts Based on Palladium Complexes with Primary Phosphines

The formation and catalytic properties of hydrogenation catalysts based on palladium(II) complexes with primary phosphines were studied. With the use of IR and UV spectroscopy, XRD analysis and GLC, it was found that the interaction of bis(acetylacetonato)palladium(II) or palladium(II) acetate with primary phosphines in an inert atmosphere resulted in the formation of polynuclear palladium complex associates mainly containing μ³-PR and a coordinated phosphine. Polynuclear palladium complexes and the palladium phosphide Pd₆P, which is formed from these complexes in an atmosphere of hydrogen, serve as supports for Pd(0) clusters. The effects of the ratio between initial components and the nature of the acido ligand at the palladium atom on the optimum conditions of catalyst formation were considered.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 609–614.Original Russian Text Copyright © 2005 by Belykh, Goremyka, Gusarova, Sukhov, Shmidt.     

Acyl- und Alkylidenphosphane. XVI. (Dimethylaminomethyliden)- und (Diphenylmethyliden)phosphane

Acyl- and Alkylidenephosphines. XVI. (Dimethylaminomethylidene)- and (Diphenylmethylidene) phosphines Alkyl- or arylbis(trimethylsilyl)phosphines 1 (R = mesityl, C₉H₁₁ a ; (CH₃)₃C b ; C₆H₅ c ; CH₃ d ) react only very slowly with dimethylformamide 2 and benzophenone 4. After repeated addition of small amounts of solid sodium hydroxide, however, the reaction-time is shortened from several months to a few days. The reactions between 1 a or 1 b and 2 yield the (dimethylaminomethylidene)phosphines 3 a and 3 b ; from 1 a and 4 mesityl-(diphenylmethylidene)phosphine 5 a is obtained. The formation of the thermally labile phosphines 3 d and 5 c is proved by NMR spectroscopy; these compounds dimerize very fast to give 2,4-bis(dimethylamino)-1,3-dimethyl- 10 d and 1,2,2,3,4, 4-hexaphenyl-1,3-diphosphetane 15 c. Similarly the lithium trimethylsilylphosphides 6 a , 6 c and 6 e (R = (CH₃)₃Si) react with 2 or 4 to form 3 a and 5 c as well as (diphenylmethylidene)-trimethyl-silylphosphine 5 e .     

Pyridinylidenaminophosphines: Facile Access to Highly Electron-Rich Phosphines

Electron-rich tertiary phosphines are valuable species in chemical synthesis. However, their broad application as ligands in catalysis and reagents in stoichiometric reactions is often limited by their costly synthesis. Herein, we report the synthesis and properties of a series of phosphines with 1-alkylpyridin-4-ylidenamino and 1-alkylpyridin-2-ylidenamino substituents that are accessible in a very short and scalable route starting from commercially available aminopyridines and chlorophosphines. The determination of the Tolman electronic parameter (TEP) value reveals that the electron donor ability can be tuned by the substituent pattern at the aminopyridine backbone and it can exceed that of common alkylphosphines and N-heterocyclic carbenes. The potential of the new phosphines as strong nucleophiles in phosphine-mediated transformations is demonstrated by the formation of Lewis base adducts with CO₂ and CS₂. In addition, the coordination chemistry of the new phosphines towards Cu^I, Au^I, and Pd^II metal centers has been explored, and a convenient procedure to introduce the most basic phosphine into metal complexes starting from air-stable phosphonium salt is described.     

Copper‐Catalyzed Reduction of Alkyl Triflates and Iodides: An Efficient Method for the Deoxygenation of Primary and Secondary Alcohols

We describe an effective method for catalytic reduction of 1° alkyl sulfonates, and 1° and 2° iodides in the presence of a wide range of functional groups. This Cu‐catalyzed reaction provides a means for the effective deoxygenation of alcohols, as demonstrated by the highly selective reduction of 1° alcohols using a triflation/reduction sequence. A preliminary study of the reaction mechanism suggests that the reduction does not involve free‐radical intermediates.     

Photochemical reduction of uranyl ion with ditertiary phosphines in dry acetone

Time-resolved transient absorption spectra have been observed using monochromatic light (=347.1 nm) from a 25 ns pulsed ruby laser. Collision between optically excited uranyl ion and ditertiary phosphines lead to photochemical reduction of uranyl ion to uranium(V) in non-aqueous medium. Stern-Volmer constants measured from lifetime measurement and quantum yields for uranium(V) formation reveal that electron transfer phenomenon competes with photophysical deactivation because of the presence of phenyl groups. Since ditertiary phosphines have two electron donating phosphorus atoms, are better reductant than monodentate phosphines in non aqueous medium.     

Studies on tetrahydrofuran solutions of manganese(II) dihalides and tertiary phosphines and their reactions with dioxygen

Solutions of Mn(THF)₂Br₂ and MnI₂ and tertiary phosphines in tetrahydrofuran at 0°C are oxidised by dioxygen or electrochemically giving deep blue-purple solutions which have identical electronic spectra. The principal band with λ_max at 570 nm has ?>9000 1 cm^?1 mol^?1. Tertiary phosphines have been shown to be oxidised to the corresponding tertiary phosphine oxides. No evidence was found for the reversible formation of dioxygen-manganese complexes.     

Ligand substitution and reduction reactions of decakis(isopropylisocyanide)dicobalt(II)

The reactions between decakis(isopropylisocyanide)dicobalt(II), present as [Co(CNCHMe₂)₅]²⁺ in solution, and three triaryl phosphines, PPh₃, P(C₆H₄Me-p)₃, and P(C₆H₄OMe-p)₃, have been studied in dichloromethane. The reactions were investigated under pseudo first-order conditions at different temperatures. A combination of conventional, stopped-flow, and infrared spectroscopy was employed in order to gain insight into the reaction mechanisms. Addition of each of the three phosphines to the Co(II) complex results in a shift in the λ _max followed by increase and/or decrease in absorbance at the new wavelength. The triaryl phosphines react in the order P(C₆H₄OMe-p)₃ ? P(C₆H₄Me-p)₃ > PPh₃. This is explained in terms of the electron-donating/π-acceptor properties of the phosphines. The reactions are proposed to proceed via a number of reaction pathways including ligand substitution, ligand rearrangement, disproportionation, and reduction.     

REDUCTION OF TERMINAL ORGANYLCHALCOGENO PHOSPHONATES AS A WAY TO PREPARE PRIMARY ORGANYLCHALCOGENO PHOSPHINES

2-Organylseleno(telluro)ethyl phosphines and 4-organylthio(seleno (telluro))butyl phosphines were prepared by reduction of diethyl 2-organylseleno(telluro)ethyl phosphonates and diethyl 4-organylthio(seleno(telluro)) butyl phosphonates with lithium aluminium hydride in diethyl ether. ¹H and ³¹P NMR spectra as well as mass spectra of the resulting phosphines were considered. Their stability in regard to the oxidation by oxygen was discussed.     

Catalytic Asymmetric Hydrophosphinylation of 2-Vinylazaarenes to Access P-Chiral 2-Azaaryl-Ethylphosphine Oxides

A chiral Brønsted acid-catalysed asymmetric hydrophosphinylation of 2-vinylazaarenes by secondary phosphine oxides is described. A variety of P-chiral 2-azaaryl-ethylphosphine oxides are synthesized with high yields and ees, of which both the substituents of phosphines and azaarenes can be flexibly modulated, underscoring an exceptionally broad scope of substrates. These adducts are valuable to asymmetric metal catalysis since the resultant P-chiral tertiary phosphines from the reduction of them are verified as a kind of effective C₁-symmetric chiral 1,5-hybrid P,N-ligands. Importantly, this catalysis platform enables the generic and efficient kinetic resolution of P-chiral secondary phosphine oxides. It thus provides an expedient approach to access the enantiomers of the P-chiral tertiary phosphine oxides derived from asymmetric hydrophosphinylation, further improving the utility of the method.     

Eine einfache methode zur synthese von organosilylphosphinen

Trimethylchlorosilane reacts with di-(t-butyl)chlorophosphine, t-butyldichlorophosphine or PCl₃ and magnesium in hexametylphosphoric triamide under formation of trimethylsilyl-di-(t-butyl)phosphine, bis(trimethylsilyl)-t-butylphosphine or tris(trimethylsilyl)phosphine respectively in high yields. This method is also useful for the synthesis of organogermanium and organotin phosphines as well as of corresponding organometal arsines.     

Preparation of L-Lyxo-Hexos-5-Ulose Through C-3 Epimerization of Bis-Glycopyranosides of L-Arabino-Hexos-5-Ulose1

Abstract

The unreported title compound and its 2,6-di-O-benzyl derivative have been prepared from methyl β-D-galactopyranoside through a sequence involving the bisglycoside methyl 2,6-di-O-benzyl-5-O-methoxv-β-D-galactopyranoside 8, the precursor of L-orabino-hexos-5-ulose, that was converted to the L-lyxo series by inversion at C-3. The inversion was achieved in acceptable yields by selective triflation, followed by displacement with benzoate, and by an oxidation/reduction sequence. Whereas 2,5-di-O-benzyl-L-lyxo-hexos-5-ulose exists entirely as a mixture of the two anomeric 1,4-furanosic forms, the unprotected hexos-5-ulose involves at equilibrium in CD₃CN/D₂O at least eight tautomers, one of which is predominant.     

A New Synthesis of Ciliapterin and Dictyopterin. Ene Reactions of (Alkenylamino)‐nitroso‐pyrimidines

A comparison of the reactivity of (acylamino)‐nitroso‐pyrimidines 1 and the alkenylamino analogue 17 in intramolecular ene reactions showed the considerably lower reactivity of 17 , leading to the pteridine 18 . Pteridin‐7‐one 11 resulting from 1 (R¹=OBn, R²=Me) was transformed into 4‐(benzyloxy)‐6‐[(E)‐prop‐1‐enyl]pteridin‐2‐amine ( 13 ) by O‐triflation, followed by reduction with LiBHEt₃, while the 4‐MeO analogue 18 was prepared by spontaneous oxidation of the initial ene product of 17 . The (alkenylamino)‐nitroso‐pyrimidine 17 was synthesized by substitution of the dimethoxy‐nitroso‐pyrimidine 16 with the allylamine 15 . Ciliapterin ( 5 ) and dictyopterin ( 7 ) were synthesized from pteridine 18 by a Sharpless asymmetric dihydroxylation.     

Phosphine and phosphinite complexes of P+ and P2

Abstract

Reduction of PCl₃ e.g. with trialkyl phosphines produces the well-known but ill-defined insoluble, amorphous, orange material approximating a phosphorus subchloride. In repeating this reduction with Ph₃P and with AlCl₃ as a third component we now obtained crystalline hexaphenyl triphosphenium tetrachloroaluminate. It may be thought to derive from the four electron cation P⁺ being complexed by two Ph₃P.     

Palladacycle-catalyzed asymmetric hydrophosphination of enones for synthesis of C*- and P*-chiral tertiary phosphines

A highly reactive and stereoselective hydrophosphination of enones catalyzed by palladacycles for the synthesis of C*- and P*-chiral tertiary phosphines has been developed. When Ph(2)PH was employed as the hydrophosphinating reagent, a series of C*-chiral tertiary phosphines were synthesized (C*-P bond formation) in high yields with excellent enantioselectivities, and a single recrystallization provides access to their enantiomerically pure forms. When racemic secondary phosphines rac-R(3)(R(4))PH were utilized, a series of tertiary phosphines containing both C*- and P*-chiral centers were generated (C*-P* bond formation) in high yields with good diastereo- and enantioselectivities. The stereoelectronic factors involved in the catalytic cycle have been revealed.     

Accessing Ambiphilic Phosphine Boronates through C−H Borylation by an Unforeseen Cationic Iridium Complex

Ambiphilic molecules, which contain a Lewis base and Lewis acid, are of great interest based on their unique ability to activate small molecules. Phosphine boronates are one class of these substrates that have interesting catalytic activity. Direct access to these phosphine boronates is described through the iridium‐catalyzed C?H borylation of phosphines. An unconventional cationic iridium catalyst was identified as optimal for a range of phosphines, providing good yields and selectivity across a diverse class of phosphine boronates (isolated as the borane‐protected phosphine). A complimentary catalyst system (quinoline‐based silane ligand with [(COD)IrOMe]₂) was optimal for biphenyl‐based phosphines. Selective polyborylation was also shown providing bis‐ and tris‐borylated phosphines. Deprotection of the phosphine boronate provided free ambiphilic phosphine boronates, which do not have detectable interactions between the phosphorus and boron atoms in solution or the solid state.     

Acyl- und Alkylidenphosphane. XXVI. 2, 4-Bis(phenylimino)-1,3-diphosphetane aus Thiocarbamoyl- und Carbamoyltrimethylsilylphosphanen

Acyl-and Alkylidenephosphines. XXVI. 2, 4-Bis (phenylimino)-1, 3-diphosphetanes from Thiocarbamoyl- and Carbamoyltrimethylsilylphosphines . Bis(trimethylsilyl)phosphines R? P[? Si(CH₃)₃]₂ 1 (R = H₃C a, H₅C₆ b, (H₃C)₃C e, H₁₁C₉ d) and phenyl isothiocyanate give insertion compounds which were identified as [CN-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphines 3 ? 2 in solution as well as in the solid state [2]. In the presence of small amounts of solid sodium hydroxide the phenyl derivative 3 ? 2b eliminates bis(trimethylsilyl) sulfane, whereas the tert-butyl 3 ? 2c and the mesityl compound 3 ? 2d show the same reaction even without a catalyst. The unstable [(phenylimino)methylidene]phosphines 6 formed first, dimerize rapidly to give 2, 4-bis(phenylimino)-1,3-diphosphetanes 7 which in solution exist as mixtures of the E and Z isomers. Via a NaOH-catalyzed elimination of hexamethyldisiloxane these cyclic phosphines 7 can also be obtained from the adducts of phenyl isocyanate and bis(trimethylsilyl)phosphines 1. Taking the thermally sufficiently stable tert-butyl derivative 7 c as an example, the temperature dependence of n.m.r. spectra is discussed in detail.